SACRAMENTO — A federal judge on Tuesday ordered California officials to prepare for the end of a six-year, court-ordered prison receivership that has cost taxpayers billions of dollars and helped force a shift of lower-level criminals from state prisons to county jails.

U.S. District Court Judge Thelton Henderson cited improving conditions in the prison system in a three-page order that says “the end of the Receivership appears to be in sight.

He appointed a receiver to run California’s prison medical system on Feb. 14, 2006, after finding that an average of one inmate a week was dying of neglect or malpractice. He cited inmate overcrowding as the leading cause, but said in Tuesday’s order that conditions have improved.

He praised the better conditions throughout the system, particularly noted during inspections of medical facilities by the prison system’s independent inspector general.

“Significant progress has been made,” Henderson wrote, citing the receiver’s own report to the federal court last week. “While some critical work remains outstanding — most notably on construction issues — it is clear that many of the goals of the Receivership have been accomplished.”

J. Clark Kelso, who took over as receiver in January 2008, looks forward to participating in the talks with state officials but declined further comment, said his spokeswoman, Nancy Kincaid.

Henderson ordered Kelso, state officials and attorneys representing inmates to report by April 30 on when the receivership should end and whether it should continue some oversight role.

Problems with inmate medical care helped prompt federal judges to require the state to ease prison crowding. That led to a shift that began last year that is sending lower-level inmates from state prisons to county jails.

The receiver’s office also was given authority to greatly expand the prison system’s medical staff and increase pay significantly.